1. Field of the Invention
The invention relates to a satellite, and a device for and a method of attaching a piggyback micro-satellite(s) payloads as a secondary payload. The deployable micro-satellite, is mounted on the nadir end of the primary satellite, preferably employing a universal adapter between the primary satellite and piggyback satellite (secondary payload).
2. Background of the Invention
In order to increase the number of payloads that can be flown with reduced costs, the concept of “hosted hardware” was developed, which infers that a parent spacecraft “host” is used as a platform on which the “hosted payload” can achieve access to space. The hosted payload may be a micro-satellite or a collection of sensors, electrical units and antenna. There are two primary ways to accomplish this task, integrating the payload into the parent satellite or integrating the payload onto the parent satellite. One approach to integrating the payload into the parent satellite involves “significant-integration,” where the payload hardware is installed during the manufacturing of the primary/“parent” spacecraft. Units are mounted directly on internal equipment shelves and spacecraft subsystems are redesigned to accommodate the specific needs of the hosted hardware. An example of this approach is the GCCS FAA payload integrated on Intelsat's Galaxy 15 spacecraft manufactured at Orbital Sciences. The disadvantage of this approach is that the flight hardware must be available in time for the assembly and test of the parent spacecraft and the non-recurring costs are high due the spacecraft redesign which must be conducted. In addition, the hosted hardware is forced to ride on the parent satellite—utilizing the parent satellite bus for power, thermal control and orbital maintenance (attitude control (pointing), station keeping and momentum dumping).
The approach of mounting a hosted payload onto the parent spacecraft offers several advantages, including: little non-recurring work is required, hardware (such as a micro-satellite) can arrive later in the program, rework of the hosted payload is much easier and switch-out of one hosted payload for another is relatively simple. To this end, several standardized Multiple Payload Adapters (MPA's) have been developed to attach to existing payload for taking advantage of the excess payload capability on launch systems.
One such approach to mounting multiple small payloads on an ASAP structure installed around the primary satellite adapter is disclosed in published patent application WO 2004/012995 A1. Another such approach developed in a cooperative venture of several U.S. government and private agencies, is the result of the ESPA (Evolved Expendable Launch Vehicle (EELV) Secondary Payload Adapter (ESPA)) program. A goal of the ESPA program is to increase the number of secondary payload launch opportunities available at a reasonable cost. Key to achieving this goal is the development of standardized adapters for launching small micro-satellites from a parent satellite, such as the ESPA adapter that can piggyback up to six secondary payloads onto a primary satellite and, thereby, take advantage of existing unused launch vehicles payload mass margin.
As explained at the Air Force Horizons Laboratory website (www.afrlhorizons.com), the ESPA adaptor is a 0.5 in. thick aluminum ring that is roughly 62 in. in diameter by 24 in. tall and can mount individual micro-satellites on one of six standardized secondary payload mounting locations found on the perimeter of the ring. The secondary payload satellites, mount radially on the ESPA adapter, are deployed from the launch vehicle at the appropriate time using a separation systems such as the Lightband, a low-shock system provided by Planetary Systems Corporation of Silver Springs, Md. Using ESPA, each secondary payload micro-satellite can have a maximum mass of 400 lbs and a dynamic envelope of 24 in.×24 in.×38 in. The ESPA adaptor is installed between the EELV payload attach fitting and the primary payload. The primary payload may have a mass of up to 15,000 lbs and requires substantial space under the fairing—since the ESPA ring is only 24 in. high, only a small amount of the total volume is taken away from the primary payload.
One of the problems with ESPA adapter ring, as disclosed in the above patent, is the weight tax of the ESPA ring itself, as the ring not only is required to carry the loads of the laterally-mounted secondary satellites (sometimes referred to as “microsats”), but also the mass of the parent or primary payload. Further, the launch penalty of the ESPA ring is not insignificant since it places extra debris into orbit. Finally, if an ESPA location is depopulated late in the program, a dummy mass model must often be flown to maintain originally-specified mass properties limitations (which is exactly what occurred on the March 2007 Atlas 5 STP mission).
Thus, there is a need to reduce the cost and increase the ease of integrating smaller secondary satellites to primary satellites (through the use of a standardized or universal adapter). Thus, it is an aspect of the present invention to overcome the problems and disadvantages of the prior art designs and methods.
It is yet another aspect of the present invention to provide a payload design that permits the use of a universal adapter for coupling together in an efficient and effective package at least one secondary payload to a primary satellite for launching the secondary payload in a certain orbit.
It is a further aspect of the present invention to provide an micro-adapter between the primary satellite and a secondary payload, which utilizes existing heritage hardware to couple and then separate the microsatellite from the parent satellite nadir-mounted micro-adaptor at the appropriate orbit.